In many medical procedures, various physiological conditions present within a body cavity need to be monitored. These physiological conditions are typically physical in nature—such as pressure, temperature, rate-of-fluid flow, and provide the physician or medical technician with critical information as to the status of a patient's condition.
One device that is widely used to monitor conditions is the blood pressure sensor. The sensor is typically included in a guide wire for intravascular measurements. A blood pressure sensor senses the magnitude of a patient's blood pressure, and converts it into a representative electrical signal that is transmitted to the exterior of the patient. For most applications it is also required that the sensor is electrically energized.
Some means of signal and energy transmission is thus required, and most commonly extremely thin electrical leads are provided inside the guide wire, which itself is provided in the form of a tube (having an outer diameter of e.g. 0.35 mm), oftentimes made of stainless steel. In order to increase the bending strength of the tubular guide wire, a core wire is positioned inside the tube. The mentioned electrical leads are positioned in the space between the inner lumen wall and the core wire.
A large flexibility of the sensor guide is advantageous in that it allows the sensor guide to be introduced into small and tortuous vessels. It should, however, also be recognized that if the core wire is too flexible, it would be difficult to push the sensor guide forward into the vessels, i.e. the sensor guide must possess a certain “pushability”. Furthermore, the sensor guide must be able to withstand the mechanical stress exerted on the core wire especially in sharp vessel bends.
A guide wire is disclosed in EP 1 475 036, assigned to the same assignee as the present invention, where a sensor element is positioned in a jacket in a sensor region of a distal part of the guide wire. The core wire has an enlarged section which extends through the jacket, and is provided with a recess or depression for reception of the sensor element.
The space within the jacket is thus very limited as it has to accommodate both the sensor element and the core wire. The outer diameter of the jacket is limited by the vessel geometry and the use of other intravascular catheters to about 0.35 mm, which makes it difficult to enlarge the outer diameter of the sensor guide wire.
Prior art guide wires may also be sensitive to bending as the jacket principally does not bend. The parts extending from both ends of the jacket may then be exposed to stress and a risk of damage to the guide wire arises.
The object of the present invention is to achieve a sensor guide wire that makes it possible to provide more space for sensor element(s) and accessories than in prior art sensor guide wires. A further aim of the present invention is to provide a sensor guide wire that reduces the risk of bending damages to the guide wire.